1. Field of the Invention
The present invention relates to graphical user interfaces for computer systems and, in particular, to head mounted displays (HMDs) for use in virtual reality (VR) and related applications.
2. Description of the Related Art
HMDs are used within VR to present pictures of a virtual world to a user, to track that users head position, and also to block out sight of the real world so that the user sees only the virtual world. Examples of patents and patent applications relating to such headsets are given in "Virtual Reality" by B. J. Spear, UK Patent Office Patent Information Monographs series PIM10, 1993, at pages 23-25. Amongst those described is U.S. Pat. No. 4,695,129 to U.S. Philips Corporation which provides a headset which enables film and television pictures to be watched in large format. Changes in user viewing direction cause that part of a larger picture displayed to the user to be changed accordingly. Another of those described is GB-A-2,201,069 of J. D. Waldern (assigned to W Industries) which shows a headset specifically designed for virtual reality applications, particularly in relation to computer games/arcade machines. Two high resolution VDU's provide stereoscopic vision to the user and it is envisaged that the system will have more than one headset such that multiple users can occupy the virtual space and interact with each other and/or with computer-generated models.
The form taken by the virtual world will depend on the intended use of the system and may, for example, comprise the interior of a building for an architectural modelling application, urban or surreal landscapes for games applications, or an environment where the user is presented with molecular models which can be manipulated. In the following, the term "virtual environment" will be used for such virtual landscapes or situations: the term "physical environment" will be used to denote the `real-world` surroundings of the user, for example sitting or standing in a room and wearing the HMD.
Once wearing the HMD, the user can become immersed in the virtual environment, causing them to forget about, or become disoriented with respect to, the physical environment. This can lead to problems with the physical environment placing restrictions on the users movement or actions, without these restrictions being apparent to the user within the virtual environment. As an example, where the system maps the users real movements (such as walking) into the virtual environment, the virtual environment may be showing to the user a clear street along which he can walk when in the real world he is in an enclosed space. This leads to the phenomenon of "glass walls" within the virtual environment which cannot be seen but are nonetheless painful to walk into. Whilst this problem might be avoided in specialist situations where a virtual environment is modelled with reference to a specific physical environment, such an approach is not possible for more general applications.
Within Location Based Entertainment (LBE) VR, the conventional approach has been to restrict the user to a small, safe area by means of tying them down or placing them in a small enclosure. This however is not a particularly practical solution for a consumer (home) environment. There is also still the problem of unexpected reactions due to interaction with the virtual environment. As an example, when immersed in a VR game playing scenario, a user may find himself confronted by a monster and their reaction is to flee via the nearest apparent exit: in the real world this could translate to the user jumping up from his chair and tripping over a connecting cable to the HMD or possibly even running into a wall.
It is therefore an object of the present invention to provide means for reducing the danger to users immersed in a virtual environment from their surrounding physical environment.